/*
 * Copyright 2015 The gRPC Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.grpc.examples.header;

import com.google.common.annotations.VisibleForTesting;
import io.grpc.ForwardingServerCall.SimpleForwardingServerCall;
import io.grpc.Metadata;
import io.grpc.ServerCall;
import io.grpc.ServerCallHandler;
import io.grpc.ServerInterceptor;

import java.util.logging.Logger;

/**
 * A interceptor to handle server header.
 */
public class HeaderServerInterceptor implements ServerInterceptor {

    private static final Logger logger = Logger.getLogger(HeaderServerInterceptor.class.getName());

    @VisibleForTesting
    static final Metadata.Key<String> CUSTOM_HEADER_KEY =
            Metadata.Key.of("custom_server_header_key", Metadata.ASCII_STRING_MARSHALLER);


    @Override
    public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
            ServerCall<ReqT, RespT> call,
            final Metadata requestHeaders,
            ServerCallHandler<ReqT, RespT> next) {
        logger.info("header received from client:" + requestHeaders);
        return next.startCall(new SimpleForwardingServerCall<ReqT, RespT>(call) {
            @Override
            public void sendHeaders(Metadata responseHeaders) {
                responseHeaders.put(CUSTOM_HEADER_KEY, "customRespondValue");
                super.sendHeaders(responseHeaders);
            }
        }, requestHeaders);
    }
}
